The methodology today for controlling the process of filling the explosive load in boreholes is based on occasionally checking the fill level of the explosive with measuring tape, and on systematically checking the stemming, which is the final length of the borehole which is left free of explosive to be filled with an inert material that confines the energy developed by the explosive at the time of detonation.
There are usually working methodologies that typically gather the information provided in the drilling reports of boreholes, allowing, to a greater or lesser extent, the detection of problems related to the ground geology, such as the presence of voids intercepted by the boreholes, ground fractures, intercalation of lower/higher hardness strata, etc.
In the case of loaded boreholes considered to be problematic due to the mentioned geology, now it is usually mandatory to use cartridge formats, either factory cartridged or in situ packing in cartridges the bulk explosive. If any doubts come up, a check is performed by means of measuring tapes ballasted with a weight to verify that the explosive is correctly filling the volume of the borehole. In occasional cases, the boreholes are cased to prevent the leakage of explosive through ground fractures or caves. However, the uncertainty today while loading an explosive of a borehole has been inherent to it from the time there are no real time images of the filling process.
Concerning the inspection of blast boreholes by means of video cameras, today this is still an occasional, often marginal task because it hinders the normal loading process, because it is based on devices the designs of which do not allow a visual inspection while loading the explosive. The problems of the devices getting snagged inside boreholes and the dirt being deposited on the viewfinder of the cameras drastically reduce the operational efficiency in current inspection systems.
The cylindrical nature of a blast borehole is particularly and substantially different from that of any other type of conduit. The main difference is that these perforations are built to be filled with explosive and to later be destroyed in the process known as the blast process. When drilling a hole directly into the rock, almost always without protections or coatings on the borehole walls, which would greatly increase the cost and delay the blast process, falling rock or rock slides are very frequent and tend to trap any object that has been introduced in the borehole. Furthermore, the loading process itself already involves pouring or introducing the explosive, whereby objects frequently remaining inside the borehole are trapped.